1. Field of the Invention
The present invention relates to a cutter wheel for forming scribe lines to cut a brittle sheet such as a semiconductor wafer, a glass plate or a ceramic plate.
2. Description of Prior Art
A prior art cutter wheel of this type has a disk wheel fabricated by grinding the circumference of a disk-like material made of cemented carbide alloy, sintered diamond or the like so as to form a generally V-shaped edge. The disk wheel is ground further around the center thereof to form a through-hole to which a rotation shaft is fitted. The wheel fabricated as mentioned above is supported in a recess of a chip holder by mounting the rotation shaft in a rotatable manner. The rotation shaft is made of iron, cemented carbide alloy, sintered diamond or the like.
In case that a cutter having a cutter wheel and a rotation shaft made of materials different from each other is used, for example, if the wheel is made of cemented carbide alloy and the shaft is made of iron, then the shaft is abraded remarkably, so that smooth rotation of the cutter wheel will become degraded. Accordingly, the quality of scribe lines becomes worse in a short time. On the other hand, if the wheel is made of cemented carbide alloy and the shaft is made of sintered diamond, the inner diameter of the through-hole for fitting the shaft becomes larger due to abrasion between the wheel and the shaft. Accordingly, smooth rotation of the cutter wheel becomes degraded though it takes a longer time than the previous example. Further such a combination of different materials makes a product expensive.
Therefore, it is conventional to make the cutter wheel and the rotation shaft by making use of the same material. However, if the same material is used, heat is generated due to abrasion between them, and seizure between them occurs. Resultantly, smooth rotation of the cutter wheel becomes degraded. If an object to be cut is a glass sheet, glass fibers are generated, thereby resulting in problems of scribe quality in a short time while scribing is performed.
An object of the present invention is to provide a cutter wheel for brittle sheets which forms scribe lines of high quality at a higher scribing speed in a longer line length to be scribed than a prior art one.
A cutter wheel according to the invention for forming scribe lines on a brittle sheet, comprises a disk with two side planes. The disk has a generally V-shaped edge formed at an outer periphery thereof and a shaft hole formed at the center thereof for inserting a rotational shaft. The cutter wheel comprises at least one groove extending from a surface of one of the side planes along the shaft hole. The groove may be provided in various ways. For example, the groove may extend in the axial direction. The groove may have a length in the axial direction of one to three quarters of the thickness of the cutter wheel. The groove may extend obliquely or spirally to the axial direction. The depth of the recesses may be set to about one to three fourths of the thickness of the cutter wheel. It is effective that the rotation shaft is made of the same material as the cutter wheel.
An advantage of the present invention is that the cutter wheel is rotated smoothly so that the scribing is performed smoothly.